Handpieces which incorporate cutting, aspirating and irrigating features are commonly used by ophthalmic surgeons during surgical operations on the eye. Because ocular surgery often involves cutting away or emulsifying unwanted tissues, as is the case in cataract surgery, the need often arises to remove tissues or fluids from the eye. To prevent damage to the eye tissue, there is also a need to irrigate the surgical site.
A number of attempts have been made to produce handpieces capable of effectively cutting, irrigating and aspirating the ocular surgical site. These instruments typically have an elongated cylindrical probe defining a cutter at their distal end, which may be inserted into the eye through an incision in the sclera. The delicate nature of ocular surgery requires that these probes be very narrow. The cutting tip of the probe is made to oscillate by means of a piezoelectric or magnarestrictive motor situated near the proximal end of the handpiece. The proximal portion of the handpiece, which must house a motor and drive mechanism, and which must be designed so as to be easily manipulated by the surgeon, is necessarily much thicker than the probe section. This difference in sizes causes the girth of the handpiece to severely narrow at a point approximately three fourths of the distance from the proximal end to the distal end of the instrument.
In order to transmit an irrigating saline solution to the probe, handpieces found in the prior art were equipped with a narrow groove cut through the solid metal outer body of the instrument. A similar groove was cut for the aspiration of fluids away from the surgical site. Due to the significant narrowing of the handpiece structure, these grooves followed a severely angular pathway through the handpiece.
A number of significant problems have been experienced with prior art handpieces. For example, the oscillating nature of the cutting tip causes cavitation of the saline solution, forming bubbles which are flushed into the eye by the flow of saline solution through the irrigation pathway. Because such bubbles impede a surgeon's view of the surgical site, they interfere with and slow down surgical procedures. Second, pulsating action, caused by the pump which flushes saline solution into the eye on the aspiration side of the handpiece, causes the eyeball to flutter during surgery and also interferes with surgical procedures.
Most importantly, the angular nature of both the irrigation pathway and the aspiration pathway makes thorough cleaning of the handpiece extremely difficult if not impossible. Thorough cleaning has now become a critical issue in light of contemplated government regulations which deal strictly with the prevention of cross tissue contamination.
In the first phase of a project by the present applicant to enhance the efficacy of prior art handpieces ("Phase I"), two significant improvements were achieved. First, the aspiration pathway was run straight through the center of the handpiece eliminating the cleaning problem caused by this formerly angular pathway. The new straight pathway can be simply cleaned by means of a straight brush or wire.
Second, rather than cutting a groove in the solid metal body or adding a tube on the outside of the piezoelectric motor or of the handpiece so as to create a pathway for irrigating saline solution, the present applicant created an outer body housing, or shell, fitting around the motor, drive mechanism, aspiration pathway and horn, such that irrigating solution could be introduced through a Luer fitting into an annular cavity between the housing and the titanium horn. This system creates a reservoir of significant volume near the site of cavitation, and thus, bubbles created by cavitation tend to migrate towards the top of the handpiece rather than being flushed out into the eye.
Though significant, the Phase I improvements did not solve the problem of how to thoroughly cleanse the irrigation pathway which, though altered from the prior art, remained angular and thus difficult to clean.
Further, in the Phase I improvement, cable connections were provided between the irrigating solution source and the irrigation pathway and the vacuum (aspiration source) and the aspiration pathway. As the handpiece is moved during surgical procedures, these cable connections may impede the surgeon's line of sight to the surgical site.